Polyester resin compositions and process of preparing same



Patented Sept. 15, 1953 POLYESTER RESIN COMPOSITIONS AND PROCESS OF PREPARING SAME John F. Davis, Stamford, Conn., assignor to American Cyanamid Company, New York, N. Y.,

a corporation of Maine N i Application January 5, 1950,

Serial No. 137,039 I l This invention relates to novel compositions of matter and, more particularly, to surface coating materials comprising unsaturated polyester resins modified with certain phenolic resin whereby one may produce a coating composition which is capable of yielding, on curing, a crater-free film. This invention further relates to surface coating materials comprising unsaturated polyester resins, which have been modified by the addition of comparatively small amounts of such butylated methylol formaldehyde resin as the butylated alkaline product produced by reacting formaldehyde with p-tertiary butyl phenol, p-secondary butyl phenol, o-tertiary amyl phenol, p-tertiary amyl phenol and bis-phenol, otherwise known by those skilled in the art as p,p'-isopropylidene diphenol, whereby the butylated methylol phenolformaldehyde resins are produced. This invention further relates to laminating materials, molding compositions and other resinous products which have exposed surface areas where cratering defects would be undesirable. I

One of the objects of the present invention is to produce a surface coatin material by the use of mixtures of unsaturated alkyd resins and compounds having at least one CH2=C group which. are capable of producing, on curing, a crater-free film while retaining all of the other desirable characteristics, which these polyester resins inherently possess. A further object of the present invention is to produce surface coating materials which have improved hardness, acid and alkali resistance, improved resistance to solvents, ex-' cellent gloss and color retention. A still further object of the present invention is to produce polyester surface coating materials, which may be baked Or air-dried and which are substantially free from all crater-like defects. These and other objects of the present invention will be set forth hereinbelow in greater detail in the further description of the present invention.

The use of polyester resins as surface coating materials has been known in the art and may be prepared according to processes set forth in the Kropa Patent 2,443,735-41 inclusive, and 2,409,633. These polyester resins have many desir'able characteristics, but under certain conditions of application and use, they display a tendency to produce crater-like defects, which tend to reduce in scope the field to which they may be applied. This defect of cratering, as it is most commonly called, is sometimes referred to as crawling or pin-holding but a more general description of the phenomenon as experienced in the application of these polyester coating compositions is in the occurrence of depressions of varying intensity which occur on the surface of the coated film giving said surface an unattractive appearance.

8 Claims. (01. 260-44) When these films are applied as a surface coatin material to a substratum base, there is sometimes formed a protuberance building up in the film around a small particle of foreign matter, Which'may be present on the surface of the material being coated or it may be present in the coating material itself in the nature of a piece of lint, dust, and the like. Sometimes these protuberances simply extend above the average plane surface of the coated film. This phenomena is normal and not too objectionable, because it is correctable by ordinary surface treatment such as by sanding or polishing. There are other times, however, when the protuberances formed around a piece of foreign matter are accompanied by and surrounded by a crater-like depression in the surface of the coated film. This surface defect is highly objectionable for a number of reasons. First, because it cannot be corrected readily by ordinary surface treatment such as by sanding or polishing. Secondly, because these crater-like depressions will reflect light and this reflection of light emphasizes and exaggerates the defect. These crater-like depressions whether caused by the presence of a piece of foreign matter or whether they are resulting from other causes may be slight or very deep. This phenomenon of cratering is-sometimes so marked that the depressions extend virtually to the substratum. Sometimes these depressions are so numerous, so aggravated, so large, and so deep that a lesser portion of the substratum urface is covered with protective film than that which is covered by l crater-like defects. Again, in these instances;

these depressions in the surface film are emphasized when reflected light causes their appearance to be of greater size and depth than what is actually the case. All of these crater-like defects are highly objectionable in surface coating materials and the elimination of these defects by the practice of the process of the present invention enhances the characteristics of these polyester resins by a still further and very important attribute.

Among the reactive resins used in the practice of this invention for interaction with the polymerizably reactive material containing the CH2=C groups are those which are derived from alpha, beta unsaturated organic acids and, therefore, contain the reactive groups present in these acids. The term acids as used herein is intended to include the anhydrides of the acids as well as the acids themselves since the former may be used instead of the acid. The term alpha, beta unsaturated organic acid as used in the art does not include acids, wherein the unsaturated group is part of an aromatic-acting radical as, for example, phthalic acid, and the same definition is adopted herein.

The resins are preferably produced by the esterification of an alpha, beta unsaturated polycarboxylic acid with a polyhydric alcohol and particularly a glycol. Although esterification of the acid with a polyhydric alcohol is perhaps one of the simplest, convenient ways of obtaining a reactive resin, I am not precluded from using resins otherwise derived from alpha, beta unsaturated organic acids. Reactiveresins'suitable for my invention are any of those containing a plurality of polymerizably reactive alpha, beta enal groups.

Preparation of the polymerizable mixture A reactive resin such, as those prepared by the esteriiication of alpha, beta unsaturated organic acids and a glycol or other polyhydric alcohol is illustrated with the reactive material containing the group CH2=C Upon adding a polymerization catalyst and subjecting the mixture to polymerization conditions such as, for example, heat, light, or a combination of both, a substantially infusible resin'is obtained.

All of these reactive substances suitable for use according to my invention for reaction with a reactive resin are characterized by the presence of the reactive group CH2==C and none of them contains a conjugated carbon-to-carbon double bond. Compounds containing a conjugated system of carbon-to-carbon double bonds are known to react with themselves or with other unsaturated compounds such as the maleic esters by a 1,2-1,4 addition mechanism such as that which has become generally known as the Diels- Alder reaction. On the other hand, compounds such as those used according to the present invention and which contain no conjugated carbon-to-ca-rbon double bonds obviously cannot undergo this type of reaction with the maleic esters. Accordingly, my invention is not directed to the use of unsaturated compounds containing conjugated systems of carbon-to-carbon double bonds. Many substances which contain a carbon-to-carbon double bond conjugated with respect to oxygen are suitable for use according to my invention, since they do not react with unsaturated alkyd resins in an undesirable manner but instead copolymerize or interpolymerize to form substantially infusible, substantially insoluble resins.

Ihe reactive allyl compounds, which may be used, are any of those compounds which contain CH2=CH-CH2- group and which do not have a boiling point below about 60 C. Of the allyl compounds which may be used, the allyl esters form a large class, all of which are suitable. The reactive allyl compounds which have been found to be most suitable are those having a high boiling point such as the diallyl esters, e. g., diallyl maleate, diallyl fumarate, diallyl phthalate, and diallyl succinate. Other allyl compounds may be used which are not necessarily high boiling. Substantially insoluble and substantially iniusible resins may be prepared by reacting or polymerizing any of the following with a polymerizabl reactive resin of the type described herein, i. e., unsaturated alkyd resins containing a plurality of alpha, beta enal groups: allyl alcohol, methallyl alcohol, allyl. acetate, allyl lactate, the allyl ester of alpha, hydroxyisobutyric acid, allyl acrylate, allyl methacrylate, diallyl carbonate, diallyl malonate, diallyl oxalate, diallyl succinate, diallyl gluconate, diallyl methylgluconate, diallyl adipate, the diallyl ester of azelaic acid, diallyl sebacate, diallyl tartronate, diallyl tartrate, diallyl silicone, diallyl silicate, diallyl fumarate, diallyl maleate, diallyl'mesaconate, diallyl citraconate, diallyl citraconate, diallyl glutaconate, the diallyl ester of muconic acid, diallyl itaconate, diallyl phthalate, diallyl chlorophthalate, the diallyl ester of endomethylene tetrahydrophthalic anhydride, triallyl tricarballylate, triallyl aconitate, triallyl citrate, triallyl phosphate, trimethylallyl phosphate, triallyl silicon, triallyl cyanurate, tetraallyl silicate, and other tetraallyl esters, the diallyl ester or" ethylene glycol dicarbonate, diallyl ester of ethylene glycol dimaleate, diallyl ester of ethylene glycol di-oxalate, diallyl ester of diethylene glycol diethylene dicarbonate, diallyl ester of ethylene glycol diethylene dimaleate, diallyl ester of diethylene glycol dioxalate, and vinyl hydrocarbons such as styrene, ortho, meta, paramethyl styrene, alpha methyl styrene, ZA-dimethyl styrene, 2,3 dimethyl styrene, isopropenyl toluene, vinyl naphthalene, 2,5-dimethyl styrene, and the like. Other reactive materials which may be employed are the methyl, ethyl, propyl, butyl, cyclohexyl. cetyl, and other alkyl esters of acrylic and methacrylic acids. Aliphatic vinyl esters may also be used including vinyl acetate, vinyl butyrate, vinyl laureate, vinyl stearate, acrolein, acrylonitrile,

methacrylonitrile, vinyl ether and the like.

The polymerization catalysts which may be used with the unsaturated polyester resins include a wide variety of materials such as diacyl peroxides, or more specifically, benzoyl peroxide, benzoyl peroxide compounded with tricresyl phosphate, technical lauroyl peroxide, 2,4-dichloro benzoyl peroxide compounded with diloutyl phthalate, p-chloro benzoyl peroxide, p-chloro benzoyl peroxide compounded with tricresyl phosphate; aldehyde peroxides such as hydroxylheptyl peroxide, dibenzaldiperoxide compounded with tricresyl phosphate; ketone peroxides such as methyl ethyl ketone peroxide in dimethyl phthalate, l-hydroxycyclohexyl hydroperoxide-1, methyl isobutyl ketone peroxide in dimethyl phthalate, methyl amyl ketone peroxide; alkyl hydroperoxides such as tertiary butyl hydroperoxide; alkyl per esters such as ditertiary butyl diperphthalate, tertiar butyl perbenzoate; alkyl acid peresters such as tertiary butyl permaleic acid, tertiary butyl perphthalic acid.

Other catalysts may be used such as the acidic peroxides, e. g., phthalic peroxide, succinic peroxide and benzoylacetic peroxide, lauric peroxide, stearic peroxide, oleic peroxide, and terpene oxides, such as ascaridole. Still other polymerization catalysts might be used in some instances such as soluble cobalt salts (particularly the lineoleate and naphthenate), p-toluene sulfonic acid, aluminum chloride, boron trifluoride.

It is customary generally to use as a concentration of catalyst a comparatively small amount, that is from about 1 part catalyst per 1000 parts of reactive mixture to about 2 parts per 100 parts of reactive mixture. If an inhibitor be present, up to 5% or even more of catalyst may be necessary according to the concentration of inhibitor. Where these compositions are used as molding and laminating materials which contain high concentrations of substances which act as inhibitors e. g., wood flour, the concentration of catalyst necessary to effect polymerization may be well above 5%.

The unsaturated alkyd resins employed in the practice of the process of my invention are preferably those having an acid number not greater than 50 although, in some cases, resins havin an acid number as high as 100may be desir able. Generally, the acid number should be as low as possible but this is sometimes controlled by practical considerations of operation such as time, temperature, and economy.

The resins should be so formulated that the carboxyl groups of the acids are reacted with the theoretical molal equivalent of the hydroxy groups of the alcohols. In this connection,- it is to be noted that the hydroxyl groups of modifying alcohols as well as the carboxyl groups of modifying acids should be included with the hydroxyl groups of the carboxyl groups of the principal reactants, the polyhydric alcohol and the alpha, beta-unsaturated polycarboxylic acid. respectively.

When glycols are reacted with dicarboxylic acids, it is preferable that the glycol be present in a molal ratio to the acid of not less than 1:2 and that the molal ratio of monohydric alcohol to dicarboxylic be not greater than 1:1. In most cases it has been found that a molal ratio of monohydric alcohol to dicarboxylic acid of 1:6 produces the best results. The same general rules apply when polyhydric alcohols other than the glycols are used such as pentaerythritol, dipentaerythritol, or polyallyl alcohols or when other polycarboxylic acids having more than 2 carboxylic groups are used. If it be desirable to introduce lower alkyl groups into the resin, this may be done by using maleic esters of monohydric alcohols, e. g., ethyl maleate. The alkyl esters will then be united with the resin by polymerization. This could not be accomplished with the saturated type of alkyd resin, e. g., phthalic acid esters or polyhydric alcohols. The preparation of the reactive resins is illustrated in the following examples, wherein the reactants are given in parts by weight.

Preparation of resin A v 98 parts of maleic anhydride are, reacted with about in excess of equimolecular proportions of ethylene glycol (68 parts) at a temperature of about 1'70-175 C. An excess of ethylene glycol is preferred because of its high volatility. The mixture is continuously agitated and carbon dioxide is introduced into the reaction chamber during the reaction thereby blanketing the surface of the reactants. After 8 to 12 hours a clear water-white resin is produced with an acid number of 35-50.

Resin A is prepared by mixing the ethylene glycol maleate resin, as prepared hereinabove, with various concentrations of diallyl maleate. The proportions vary between 10% of the ethylene glycol maleate resin to 90% of the diallyl maleate; 30% resin, 70% diallyl maleate; 50% ethylene glycol maleate resin and 50% diallyl maleate; 70% ethylene glycol maleate resin and 30% diallyl maleate; 90% ethylene glycol maleate resin and 10% diallyl maleate. These mixtures comprise the composition of resin A.

The following results were attained after ouring resin A in its various proportions for 4 days at 58 C.

. Diallyl Resin maleate, Result 7 percent percent 10 90 Clear-soft. 30 70 Clear-semi-hard gelled after 24 hours.

50 50 D0. 70 30 Do. 90 10 D0.

6 Similar resultsare obtained substituting diallyl fumarate and diallyl phthalate for the diallyl maleate.

Preparation of resin B 106 parts of diethylene glycol and 98 parts of maleic anhydride were separately vacuum distilled into a reaction chamber, and the mixture was stirred mechanically while carbon dioxide gas was introduced over the surface of the resin to exclude air and to remove water that was formed in the esterification. The reaction was conducted at 170 C. for a period of from 8-12 hours yielding a resin of acid number of 35-50.

The diethylene glycol maleate resin, with an acid number of 50 as produced hereinabove, is mixed with diallyl phthalate in a plurality of ratios, based on percentages of the diethylene glycol maleate resin and diallyl phthalate totalling 100% in the mixture. The proportions of the resin to the polymerizable monomer vary between 10% of the former to 90% of the latter to 60% of the former to 40% of the latter. Each of these mixtures is identified as Resin B, containing about 0.4% of benzoyl peroxide. In order to illustrate the contrast between the use of the resin with the monomeric material, and the monomeric material alone, a plurality of samples of Resin B with varying ratios of resin to monomer were heated at 44 C. for 24 hours, and then at 100 C. for 3 hours, with the results shown hereinbelow.

Resin Diauyl Result percent phthlate,

percent 24 hours 27 hours 0 100 Liquid. Liquid. 10 90 Slightly opaque gel. Slightly opaque gel. 20 do. Do. 30 70 do. Do. 40 60 do. Do. 50 50 Clear gel Clear gel. 60 40 do Do.

Resin C ffiggf Ethylene Result at C. at- I phthalioglycol 32??? fumaric maleate a 6 resin 11 min. 20 min.

Parts Parts Parts 60 0 40 Tack-free... Dry. 30 30 40 .do Dry. 10 50 40 Tacky. Dry.

It has been pointed out hereinabove that the phenolic resins which are to be used as modifiers for these polyester resins for the purpose of eliminating the tendency of these polyester resins to crater when applied as surface coating materials are butylated p-tertiary butyl phenolformaldehyde resin, butylated p-secondary butyl phenol-formaldehyde resin, butylated o-tertiary amyl phenol-formaldehyde resin, butylated ptertiary amyl phenol-formaldehyde resin, and

propionaldehyde, benzaldehyde, furfural and the like. To efiect butylation, one may use n-butanol, secondary butanol or mixtures of same.- In order to illustrate the procedure for the preparation of these'phenolic resins to be used in the practice of the process of the instant invention, the following examples are set forth for the purpose of illustration only. All parts are parts by weight.

Resin D Charge 456 parts of bis-phenol and 800 parts of 'a 37% aqueous solution 01 formaldehyde into a suitable reaction chamber and heat with agitation to about 80 C. until the solution is clear. Allow the solution to cool until the bis-phenol begins to crystallize out (at about 50 C.). Thereupon 18 parts of a 25% aqueous solution of 'NaOH are added slowly. The temperature is lowered to about 40 C. and held at that temperature forapproximately 72 hours. The pH of the solution is then adjusted to about 3 by the addition of dilute sulfuric acid. A quantity of water equal to the volume of solution present in the reaction vessel is added, the mixture stirred for a prolonged period of time and permitted to separate into two immiscible layers The upper aqueous layer is then removed. n-Butanol' is then added in an amount sufficient to give a ratio of one part butanol for each two parts of bisphenol present in the solution. 10 parts of xylol are added to the solution which is then heated to reflux in a suitable reaction chamber equipped with a water trap. About rec parts of waterwill be distilled off. Additional quantities of butanol should be added from time to time in order to maintain the reflux temperature at less than 135 C. The resin is thensteam distilled to remove any remaining free bis-phenol and then vacuum treated at 135 C. The final resin is low melting and clear.

Resin E Introduce into a suitable reaction chamber equipped with thermometer and stirrer, 600 parts oi a p-tertiary butyl phenol, 488 parts of a 37% aqueous formaldehyde solution and 250 parts of naphtha. The ingredients are stirred to effect complete mixing and 300 parts of a 10% sodium hydroxide solution are added and the reaction mixture is then heated to refluxK85-90" CL); The reaction mixture is held at reflux until it becomes cloudy (about 2 hours). The pH is adjusted to 4-5 with dilute hydrochloric acid. The reaction chamber may then be filled with water and-permitted to separate into two immiscible layers, whereupon the lower aqueous layer is removed. The naphtha is then removed by vacuum distillation. Charge 1200 parts of n-butanol and 5-10 parts of xylol into the reaction vessel. The reactants are then refluxed until no further sign of water appears in the reflux stream. In the course of this reaction, the batch temperature will generally rise to temperatures above 100 C. The maximum reflux temperature should not exceed 135 C. Upon completion of the reaction, the batch is steam distilled to remove any free p-tertiary butyl phenol, which may still be presexit, while holding the batch temperature at about C. Excess water is removed by vacuum distillation. Although the examples set forth hereinabove in Resin D and Resin E show processes for the butylation of these particular phenol-formaldehyde resins-other alkylation processes may be carried out by use of such alcohols as methanol, ethanol, propanol, isopropanol, amyl alcohol,and isoamyl alcohol. It is preferred, however, to use n-butanol or secondary butanol. The amount of butanol, which may be used in the butylation step is not critical. It is sunicient if there is an excess of butanol present, which will insure complete reaction and revent or tend to prevent the resiniflcation of the methanol groups. Sumcient xylol is generally added in order to accomplish the removal of the water as it is formed. The water accumulation, in the course of the reaction, causes a binary mixture to form which when condensed causes the water to separate from the xylol and can then be removed as the lower layer. In order to prepare solutions of the butylated phenolic resin in the unsaturated polyester resins, it is necessary only to pulverize said phenolicresin when it is added to the unsaturated polyester resins such as that prepared according to the process of Resin A with continuous agitation. This mixture is heated on a water bath (50-60 C.) until a solution of the phenol resin in the unsaturated polyester resin is obtained. This resin mixture is cooled and stored in a cool place until ready for use. When it is desired to use the liquid phenolic resin such as that prepared according to the process set forth in Resin E, it is generally only necessary to add the liquid resin to the polyester resin with continuous agitation until a complete solution is obtained. By warming this mixture on a water bath, one may hasten the solution of the phenolic resin in the polyester resin. As a still further modification of the addition of the phenolic resin, one may add the phenolic resin, prepared according to the processes of either Resin D or Resin E, to the unsaturated polyester resin during the preparation of the latter. If this modification is desired, the phenolic resin may be added. after the monomeric material, such as di allyl phthalate, has been added to the unsaturated alkyd, and blended for a period of time and cooled to 110420 C. At this point, the phenolic resin may be added and said resin will dissolve as the polyester resin is further cooled to room temperature. As a still further modification of the incorporation of the phenolic resin into the polyester resin, one may dissolve said phenolic resin in the monomer, such as styrene, prior to its addition to the unsaturated alkyd resin. Heating may be required to bring about the solution of the phenolic resin in these monomers, especially those having lower solvent power for this material. A still further modification of the process of incorporating the phenolic resin into the polyester resin can be accomplished where it is desired to use the polyester resin in the form of a solution in a suitable solvent such as toluene, ethyl alcohol, or ethyl acetate. In this instance, the phenolic resin may be dissolved in a suitable solvent and added to the unsaturated polyester solution with agitation until the solution is completed. I I I The following examples are set forth for the purpose of illustrating the formulations for coating compositions prepared in accordance with my discovery. All parts are parts by weight.

9 Example 1 1 Parts Unsaturated polyester (Resin A) 100 Butylated p-tertiary butyl phenol-formaldehyde (Resin E) 0.75 Cobalt (as 6% naphthenate) 0.33 Methylol amyl ketone peroxide 1.6

and 300 F. for periods of time varying between about 60 minutes at the lower temperature to about minutes at the higher temperature one obtains a hard tack-free clear film, which is completely free or very substantially free of all crater-like defects.

Example 2 Parts Unsaturated polyester resin (Resin B) 100 Butylated p-tertiary butyl phenol-formaldehyde (Resin E) 0.75 Titanium dioxide 100 Solvent (ethyl acetate) 55 l The above constituents were ground in a pebble mill for about 36 hours and thereafter 0.33 part cobalt (as 6% methyl amyl ketone peroxide were blended into theinitial mixture and additional solvent is added to give the coating material the desired application viscosity when this coating material is applied to a substratum base and cured at temperatures ranging from about 150 Frto 300 F. for periods varying from about 60 minutes at the lower temperature to about 10 minutes at the higher temperature, a White gloss enamel surface is obtained which is completely free or substantially; completely free of all crater-like defects.

The above formulation may be varied in a number of diiferent ways by the addition of modifying materials, difierent pigments, fillers, catalysts, driers and the like.

Example 3 Parts Unsaturated polyester (Resin C) 100 Butylated p-tertiary butyl phenol-formaldehyde (Resin E) 0.75 Titanium dioxide 133 Lithopone 133 Talc 133 These constituents may be blended and prepared in the same manner as that set forth hereinabove in Example 2 to produce a white primer surface and when so used is completely free or substantially completely free of all crater-like defects.

In the formulation of the phenolic resins, to be used to modify the polyester resins in keeping with the instant invention, it is generally desired to use a mol ratio of phenol to formaldehyde of 1:1.5, respectively. It is possible, however, to vary the mol ratio of the particular substituted phenol to formaldehyde within the range of 1:1 to 1:2, respectively. The amount 01' phenolic resin required to effect this improvement, which I have discovered, is within the range of 0.25%

cobalt naphthenate) and 1.66 parts 1 to about 1.25% by weight based on the total weight of the polyester resin selected. This range of percentages gives optimum results. However, it is possible to use as little as 0.01% of the phenolic resin by weight based on the Weight of the polyester resin but when this amount is used, the improvement in the surface characteristics are comparatively slight. By using percentages of 0.05% and 0.10%, one effects increasingly improved characteristics. It is not until. one reaches 0.25% phenolic resin that one begins to realize the marked effectiveness of result, which these particular buty'lated phenolic resins .are capable of producing, This effectiveness increases to a content of 1%. Thereafter and up to 1.25%, the increase in effectiveness is not appreciable if the polyester films produced with this amount of modifier have already reached substantlally optimum surface conditions. When the amount of the phenolic resin exceeds 1.25% by weight based on the total weight of the polyester resin, signs of incompatibility begin to appear in some polyester resins. In other polyester resins, it is possible to use up to 5% of the phenolic resin Without experiencing any incompatibility. Above 5% striations sometimes begin to appear and incompatibility is one of the imcomposition comprising a polymerizable mixture (c) a catalyst for accelerating the copolynierization of a and b, and (2) 0.01 %-5% by weight of a butylated phenol-formaldehyde resin wherein the phenol is selected from the group consisting of p,p'-isopropylidene diphenol, p-tertiary butyi phenol, p-secondary butyi phenol, p-tertiary amyl phenol, and o-tertiary amyi phenol and wherein sald ailryd resin contains a plurality of producing, on curing, a crater-free film, comd of (1) a polyester of a and b, and (2) 0.01 %-5% by weight a butylated p-tertiary amyl phenol-formaldehyde resin and wherein said alkyd resin contains a plurality of polymerizably reactive alpha, beta enal groups.

3. A surface coating composition, capable of producing, on curing, a crater-free film, comprising a compatible blend of (1) a polyester resin composition comprising a polymerizable mixture of (a) a polymerizably reactive unsatu l rated alkyd resin, (b) a, compatible polymerizably reactive material having at least one CH2=C group and (c) a catalyst for accelerating the copolymerization of a and b, and (2) 0.01%-5% by weight of butylated o-tertiary amyl phenol-formaldehyde resin and wherein said alkyd resin contains a plurality of polymerizably reactive alpha, beta enal groups.

4. A surface coating composition, capable of producing, on curing, a crater-free film comprising a compatible blend of (1) a polyester resin composition comprising a polymerizable mixture of (a) a polymerizably reactive unsaturated alkyd resin, (12) a compatible polymerizably reactive material having at least one CH2=C group and (c) a catalyst for accelerating the copolymerization of a and b, and (2) 0.01%-5% by weight of a butylated p,p'-isopropylidene diphenol formaldehyde resin and wherein said alkyd resin contains a plurality of polymerizably reactive alpha, beta enal groups.

5. A surface coating composition, capable of producing, on baking, a crater-free film, comprising a compatible blend of (1) a polyester resin composition comprising a, polymerizable mixture of (a) a polymerizably reactive unsaturated alkyd resin, (b) a compatible polymerizably reactive material having at least one CH2=C group and (c) a catalyst for accelerating the copolymerization of a and b, and (2) 0.25 %-1.25% by Weight of a butylated p-tertiary butyl phenolformaldehyde resin and wherein said alkyd resin contains a plurality of polymerizably reactive alpha, beta enal groups.

6. A surface coating composition capable of producing, on baking, a crater-free film, comprising a compatible blend of (1) a polyester resin composition comprising a polymerizable mixture of (a) a polymerizably reactive unsaturated alkyd resin, (b) a compatible polymerizably reactive material having at least one CH2=C group and (c) a catalyst for accelerating the copolymerization of a and b, and 0.25%- 1.25% by weight of butylated p-tertiary amyl phenol-formaldehyde resin and wherein said alkyd resin contains a plurality of polymerizably reactive alpha, beta enal groups.

12 '7. A surface coating composition capable of producing, on curing, a crater-free film comprising a compatible blend of (1) a polyester resin compriisng a polymerizable mixture of (a) a polymerizably, reactive unsaturated alkyd resin, (b) a compatible, polymerizably reactive material having at least one CH2:C group and (c) a catalyst for accelerating the copolymerization of (a) and (b) and (2) 0.05%-5% by Weight of a butylated phenol-formaldehyde resin, wherein the phenol is selected from the group consisting of p.p'-isopropylidene diphenol, p-tertiary butyl phenol, p-secondary butyl phenol, p-tertiary amyl phenol, and o-tertiary amyl phenol and wherein said alkyd resin contains a plurality of polymerizably, reactive alpha, beta enal groups.

8. A surface coating composition capable of producing, on curing, a crater-free film comprising a compatible blend of (1) a po yester resin comprising a polymerizable mixture of (a) a polymerizably, reactive unsaturated alkyd resin, (b) a compatible, polymerizably reactive material having at least one CH2=C group and (c) a catalyst for accelerating the copolymerization of (a) and (b) and (2) 0.25%-1.25% by weight of a butylated phenol-formaldehyde resin,

wherein the phenol is selected from the group consisting of p,p'-isopropylidene diphenol, p-ter tiary butyl phenol, p-secondary butyl phenol, p-tertiary amyl phenol and o-tertiary amyl phenol and wherein said alkyd resin contains a plurality of polymerizably reactive alpha, beta enal groups.

JOHN F. DAVIS.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES The Merck Index, 6th ed., 1952, Merck 8: Co., Rahway, N. J., page 153. 

1. A SURFACE COATING COMPOSITION, CAPABLE OF PRODUCING, ON CURING, A CRATER-FREE FILM, COMPRISING A COMPATIBLE BLEND OF (1) A POLYESTER RESIN COMPOSITION COMPRISING A POLYMERIZABLE MIXTURE OF (A) A POLYMERIZABLY REACTIVE UNSATURATED ALKYD RESIN, (B) A COMPATIBLE POLYMERIZABLY REACTIVE MATERIAL HAVING AT LEAST ONE CH2=X< GROUP AND (C) A CATALYST FOR ACELERATING THE COPOLYMERZATION OF A AND B, AND (2) 0.01%-5% BY WEIGHT OF A BUTYLATED PHENOL-FORMALDEHYDE RESIN WHEREIN THE PHENOL IS SELECTED FROM THE GROUP CONSISTING OF P,P''-ISOPROPYLIDENE DIPHENOL, P-TERTIARY BUTYL PHENOL, P-SECONDARY BUTYL PHENOL, P-TERTIARY AMYL PHENOL, AND O-TERTIARY AMYL PHENOL AND WHEREIN SAID ALKYD RESIN CONTAINS A PLURALITY OF POLYMERIZABLY REACTIVE ALPHA, BETA ENAL GROUPS. 